1. Field of the Invention
This invention relates to articulated joints, and particularly to articulated joints in tilt-adjustable steering column assemblies.
2. Brief Description of The Related Art
The articulating joints used in tilt-adjustable steering columns have not deviated substantially since they were first introduced. Essentially a lower housing is pivotally coupled to an upper housing by two diametrically opposing horizontal pins which are threaded into one of the housings and have a bearing surface at an intermediate point along the shaft for pivotally supporting the other housing. The weight of the upper housing attached to the steering wheel, whether the inner or outer housing, places a load on the bearing surface of the pins. As the upper housing rotates with respect to the lower housing, torque is produced by the tilting action on the bearing surface which can loosen the pins. As the pivotal coupling loosens, substantial backlash results in the coupling. If allowed to progress, the entire assembly can fail, resulting in possible loss of control of the vehicle and injury to the operator. Examples of articulating joints in tilt-adjustable steering columns having the construction described above are disclosed in U.S. Pat. Nos. 4,594,909 (FIG. 4) and 4,903,540 (FIG. 3).
Variations of this aforementioned assembly have simply reversed the location of the bearing surface on the pins. For example, the threads are located along the cylindrical shaft of the pin, and the cylindrical bearing surface is located toward the end of the pin. For example, see U.S. Pat. Nos. 5,605,351 and 4,925,210. In this situation, the torque produced by the tilting action of the respective components produces the same result. The angular forces produced by the torque, coupled with the arm of the arc from the axis of the respective pin, tends to rotate the pin out of the threaded coupling to loosen the connection with the same possible results.
An additional disadvantage resulting from the conventional pivotal coupling described above is the long term wear on the bearing surfaces of the pins. Irrespective of the relative position of the upper and lower housings, the load on the bearing is either along the upper or lower surface. Because most of the friction in the coupling takes places at either of these locations, the bearing surfaces tend to become eccentric. As a result, the coupling becomes unstable producing substantial backlash and the possibility of failure.
The various embodiments of the articulating joint used in the steering column embodying the instant invention substantially reduce the backlash associated with the loosening of the pins making the pivotal connection. Test results have shown that with time, the coupling in the instant invention actually improves.